A user can operate a touch panel display device or the like to input an operation signal to an information processing unit such as a processor circuit in a portable telephone terminal apparatus such as a smartphone. The information processing unit performs data processing in response to the operation signal to create given image data. Then, the information processing unit causes a display device of the portable telephone terminal apparatus to display an image of the image data.
Incidentally, while the user looks at an image displayed on the display device, the user sometimes uses the telephone function and application software for voice call of the portable telephone terminal apparatus (the telephone function and the application software for voice call are hereinafter referred to collectively as voice call function, and the application software is hereinafter referred to as application). This is, for example, a case in which, in a state in which an image by a particular application is displayed on the display device, a call request is received from a different user or a like case. In order to make it possible for the user to use the voice call function, the portable telephone terminal apparatus includes a speaker and a microphone. It is assumed that, in such a situation as just described, the voice call function is started up while the particular application is in an activated state, and after the voice call is started, while the voice call function operates on the background, the particular application that displays an image operates on the foreground. In this case, in order to listen to voice call sound of the different user issued from the speaker, the user of the portable telephone terminal apparatus would hold the portable telephone terminal apparatus in the proximity of an ear of the user and it is difficult to visually observe the display substance of the display device. Therefore, even if the substance displayed as a result of processing of the particular application changes during the voice call, it may be difficult for the user to recognize the change. As a related art, for example, Japanese Laid-open Patent Publication No. 2008-167373 is disclosed.
In a telephone terminal apparatus including an image display device, within a period within which a user talks using the voice call function the telephone terminal apparatus includes, it may be difficult for the user to visually observe the image display device and to recognize an update of an image occurring within the period. A similar problem occurs also when the user holds the telephone terminal apparatus in the proximity of an ear in order to listen to sound of voice, music or the like reproduced from a speaker in addition to the voice call sound.